its basically an incentive to get you "bundled", whether they make or loose over the initial 24 month restriction is really not the issue,
Bundling makes customers "sticky" in the current Sales and Marketing lingo, and less likely to churn ( as they have to organise multiple separate transactions if they want to move away from you, and this gives the utility a better change to try to keep them)...
its also a good draw for customers who need a new appliance (ie moving to a new home/flat) and are unlikely to be in relationship with an existing Utility,
T/Power will have run the numbers on the back end of it and would not be doing it unless it made them $$